1. Field of the Invention
The present invention relates to a secondary battery, and more particularly to, a secondary battery having an electrode assembly on which finishing tapes forming passages are attached.
2. Description of the Related Art
Lithium secondary batteries are classified, according to their electrolytes, into lithium ion secondary batteries using liquid electrolytes and lithium polymer batteries using polymer electrolytes. A lithium ion secondary battery is manufactured by sealing a jelly-roll type electrode assembly, which is a power generation source, with a can or a pouch type cover, and then by injecting an electrolyte inside the cover. In particular, in the lithium ion secondary battery using a can as the cover, after an electrolyte is injected through an injection hole formed in the cover, the injection hole is closed. For a normal operation of the battery, it is necessary to completely fill electrolyte in the electrode assembly.
Lithium ion secondary batteries are also classified according to their shapes, which includes cylinder type batteries and rectangular plate-like square type batteries. A jelly-roll type electrode assembly is wound such that two electrode plates and two separators are alternately disposed. A finishing tape is attached around the outer surface of the electrode assembly so that the electrode assembly cannot be loosened.
However, this type of structure of an electrode assembly around which a finishing tape is attached has the following shortcomings.
First, it hampers smooth filling of the electrolyte. In other words, the finishing tape, which is attached to the entire outer surface of the electrode assembly, impedes the flow of the electrolyte downward inside the can during injection of the electrolyte. Accordingly, the electrolyte is likely to be filled only at an upper portion of the electrode assembly, increasing process time and lowering productivity.
Second, it prevents radiation of heat. A large amount of heat is generated in the electrode assembly during charge and discharge processes of the battery, and the finishing tape attached to the entire surface of the electrode assembly prevents dissipation of the heat through the surface of the electrode assembly.
Third, it causes deformation of the battery. The electrode assembly expands during discharge of the battery. In this case, the finishing tape attached to the entire surface of the electrode assembly excessively presses the electrode assembly, abnormally deforming the shape of the battery.